1. Field of the Invention
This disclosure relates to fuel cutoff valves each attached to a fuel tank of a vehicle such as gas vehicle.
2. Description of the Related Art
A vehicle such as gasoline vehicle has a fuel tank provided with a fuel cutoff valve. The fuel cutoff valve allows fluid communication between an inner space of the fuel tank and outside of the fuel tank (for example, adsorbent canister) in a normal condition, and prevents fuel from flowing outside the fuel tank in conditions that the vehicle is inclined or overturns, etc.
Japanese Laid-Open Patent Publication No. 2005-194957 discloses a conventional fuel cutoff valve as shown in FIGS. 13 an 14. FIG. 13 shows a cross-sectional view of the fuel cutoff valve in an open state. FIG. 14 is a cross-sectional view of the fuel cutoff valve in a closed state. As shown in FIG. 14, a fuel cutoff valve 101 is attached to an upper section of a fuel tank 110 and is composed of a case 102 and a float valve body 103. The case 102 defines a float chamber 107 and a connection path 102b therein. The float chamber 107 is fluidly communicated with an inner space of the fuel tank 110. The connection path 102b is fluidly communicated with an upper end of the float chamber 107 via a communication opening 104a. The connection path 102b is fluidly communicated with an adsorbent canister. The float valve body 103 is disposed in the float chamber 107 such that the float valve body 103 can move upwardly and downwardly. When the float valve body 103 is at a lower position, the communication opening 104a is open (FIG. 13), whereas when the float valve 103 is at an upper position, the communication opening is closed (FIG. 14). A valve spring 105 is disposed between the float valve body 103 and a bottom wall 102d for the float chamber 107. The valve spring 105 biases the float valve body 103 upwardly in order to assist upward movement of the float valve body 103 due to buoyant force. However, spring force of the valve spring 105 is too weak to elevate the float valve body 103 by oneself. The bottom wall 102d for the float chamber 107 has a plurality of communication holes 102a for fluidly communicating the float chamber 107 with the inner space of the fuel tank 110. In the fuel cutoff valve 101, an upper space 108 is defined between an upper wall for the float chamber 107 and an upper surface of the float valve body 103 (FIG. 13), and a lower space 109 is defined between the lower wall 102d for the float chamber 107 and a lower surface of the float chamber 103 (FIG. 14). The float valve body 103 defines communication passages 103b therethrough.
When a vehicle equipped with the fuel cutoff valve 101 is in a normal condition (FIG. 13), the float valve body 103 is at the lower position and the communication opening 104a is open. Thus, fuel vapor vaporized in the fuel tank 110 can flow through the communication holes 102a, the communication passage 103b, the float chamber 107, the communication opening 104a and the connection path 102b toward the outside of the fuel tank 110. When the vehicle overturns or banks, the liquid fuel flows into the float chamber 107 via the communication holes 102a. Thus, the float valve body 103 moves upwardly due to buoyant force such that the communication opening 104a is closed (FIG. 14). Accordingly, because fluidly communication between the float chamber 107 and the connection path 1026 is blocked, it is able to prevent the fuel from flowing out of the fuel tank 110.
When the vehicle returns to the normal condition, the fuel in the float chamber 107 flows into the fuel tank 110 via the communication holes 102a. Thus, the flow valve body 103 moves downwardly, and the communication opening 104a is opened (FIG. 13).
In order to reduce unintentional movement of the float valve 103 in a horizontal direction, a space 112 between the float valve 103 and an inwardly facing surface of the case 102 is preferably narrowed. However, when the space 112 is narrowed, the fuel is likely to remain in the space 112 during discharge of the fuel from the float chamber 107. Thus, there has been a need for improved fuel cutoff valve.